Inspection system for repairs or joints of composite material applied to a structure

ABSTRACT

This invention is related to inspection techniques for composite joints and repairs. In this scenario, this invention provides a system for inspecting a repair or joint made of composite material applied to a structure, comprising at least one element that excites or is excited ( 2, 10 ) by a thermal and/or vibrational stimulus, with at least one exciter or excitable ( 2, 10 ) element being embedded in the repair ( 1 ) or joint.

FIELD OF INVENTION

This invention is related to material inspection techniques. More specifically, this invention is related to inspection techniques for composite joints and repairs.

BASICS OF THE INVENTION

Use of composite materials in several areas of industry is on the rise. The aerospace sector is the heaviest user of this type of material. However, industries in the oil and gas and energy sectors have also been accompanying this trend, especially because of the material's high strength/weight ratio, immunity to corrosion and the possibility of “cold” application of these materials. In the oil and gas industry, the possibility of cold application to joints and repairs is very attractive because it eliminates the requirement to isolate the workspace and ensures that it is free of risks of combustion and explosion.

Two classes of applications for composite materials are establishing themselves in the oil and gas and energy industries: repairs with composite materials and structural elements entirely produced from composite materials. The first involves the application of a layer of composite material over a metallic structural element, either as a barrier to corrosion or as structural reinforcement. The second class mainly involves pressure pipes and vessels made entirely of composite materials.

In the oil and gas and energy sectors, the history of failures with composite materials is related mainly to assembly defects or issues during the application of coatings in the field. This is typically the case of repairs and protective coatings for composite materials and joints between pipes made of composite materials.

In both cases, the application conditions are normally not favorable, resulting in a higher probability of defects, such as: adhesion failures (on the metal-composite and composite-composite interfaces); delamination (adhesion failures between the layers of a composite material); inclusions (presence of blisters and foreign bodies between the layers of a composite material) and non-homogeneity in the distribution of the fibers in the composite material. There may also be structural defects resulting from the component manufacturing process.

Defects in coatings and protective repairs may compromise the efficacy of protection or structural reinforcement. If not detected and corrected, defects in joints and unions of composite pipe structures can deteriorate and lead to operational failures, resulting in a risk of leaks.

The use of composite repairs in metallic pipes performed in the field has been growing, although a lack of effective field inspection techniques means its use is still very limited. Thus, in the current state of use of these materials, inspection of coatings and repairs applied in the field, as well as unions and joints in composite structures, is essential.

Shearographic and thermographic equipment is capable of undertaking non-destructive inspection of composite materials. However, detection of internal defects using shearography or thermography requires the generation of a thermal gradient (excitation) inside the composite material. In addition to thermal excitation, shearography can also be used with vibrational excitation in order to detect defects.

The current state of the techniques comprises several repair monitoring techniques where sensors are inserted inside the repair in order to continuously monitor it.

Document ES2368541B1, for example, reveals a repair procedure for metallic aircraft structures using composite material. This method comprises the insertion of fiber optics between the structure of the aircraft and the composite repair, thus enabling the integrity of the repair to be inspected in a practical manner.

Document CN101561400B also contains a method for repairing structural damage in an aircraft using composite material by inserting fiber optics into the repair in order to monitor the integrity of the repair by fiber Bragg grating (FBG). With this technique, it is possible to monitor the repair in real time.

However, continuous monitoring techniques (online) for the repair are quite expensive, as they require a fully dedicated monitoring system.

Thus, in the current state of the art, there is a necessity for a low-cost technique that enables the inspection of repairs or joints of composite material by means of thermal and/or vibrational excitation.

As will be described in greater detail below, this invention intends to solve the problem of the state of the technique described above in a practical and efficient manner.

SUMMARY OF THE INVENTION

The primary objective of this invention is to provide a low-cost and effective inspection system for a repair or joint made of composite material applied to a structure.

In order to achieve the aforementioned objective, this invention provides an inspection system for a repair or joint made of composite material applied to a structure, comprising at least one element that excites or is excited by a thermal and/or vibrational stimulus, with at least one exciter or excitable element being embedded into the repair or joint.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description presented below refers to the attached figures and their respective reference numbers.

FIG. 1 is a cutaway diagram of the first embodiment of the system of this invention in a composite repair in a pipeline.

FIG. 2 is a detailed cutaway diagram of the first embodiment of this invention.

FIG. 3 is a side view of a second embodiment of the system of this invention in a composite repair in a pipeline.

FIG. 4 is a cutaway diagram of a third embodiment of the system of this invention in a composite repair in a pipeline.

FIG. 5 is the result of a thermographic inspection from the internal excitation promoted by the system in accordance with the first embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Firstly, it should be emphasized that the following description is a preferred embodiment of the invention. However, as will be evident to any person skilled in the art, this invention is not limited to this specific embodiment.

The system for inspecting a repair or joint made of composite material applied to a structure, according to this invention, comprises at least one element that excites or is excited by a thermal and/or vibrational stimulus, with at least one exciter or excitable element being embedded in the repair or joint.

FIG. 1 is a cutaway diagram of a first embodiment of the system of this invention in a composite repair 1 in a pipeline 3. In this first embodiment, applied to a composite repair 1, the excitable element is at least one layer of material that is excited by a thermal and/or vibrational stimulus. More preferably, this layer excited by a thermal and/or vibrational stimulus is a layer of carbon fiber 2.

Depending on the height of the repair, the use of two or more carbon fiber layers 2 may be necessary to ensure excitation throughout the thickness of the composite repair 1. In the first embodiment, illustrated in FIG. 1, two layers of carbon fiber 2 are used.

The system of this invention may also comprise at least one thermal connector 4 adapted to connect each of the carbon fiber layers to a power source 5. Accordingly, the carbon fiber layers are thermally excited by at least one thermal connector 4.

Preferably, the first electric cable 6 connects the thermal connector 4 to the power source 5. Additionally, and also preferably, the second electric cable 7 connects the power source 5 to the electricity network (not shown).

FIG. 2 is a detailed cutaway diagram of the first embodiment of this invention. During thermal excitation (heating), the repair 1 is observed with a non-destructive inspection system 18, as illustrated in FIG. 2. Non-destructive inspection may be conducted by means of a shearographic system, a thermographic camera or both.

FIG. 2 also illustrates the bi-directional thermal flow 17 generated by the carbon fiber chambers 2 embedded in the composite repair 1. The individual heating of each layer assists in estimating the depths at which the defects are located 15, 16.

FIG. 3 is a side view of a second embodiment of the system of this invention in a composite repair 1 in a pipeline 3. In this first embodiment, applied to a composite repair 1, the excitable element is at least one piezoelectric actuator embedded in the composite repair 1, where the actuator is adapted to receive an external signal and vibrate at least at a certain frequency. More preferably, a set of piezoelectric actuators 10 are embedded in the extremities of the composite repair 1, as illustrated in FIG. 3.

The second embodiment of the system of this invention may also comprise at least one vibrational connector 11 adapted to connect and send an external signal to each of the actuators. Accordingly, each of the piezoelectric actuators 10 is connected to the adjacent actuators. Furthermore, the vibrational connector 11 receives the signal from an amplified signal generator 12 for harmonic vibration at varying frequency. The signal sent to the vibrational connector 11 is distributed to the piezoelectric actuators 10.

Optionally, as illustrated in FIG. 3, two vibrational connectors 11 are provided, where each of them distributes the signal from an amplified signal generator 12 to a certain set of piezoelectric actuators 10.

As in the first embodiment, preferably the first electric cable 6 connects the vibrational connector 11 to the amplified signal generator 12. Additionally, and also preferably, the second electric cable 7 connects the amplified signal generator 12 to the electricity network (not shown).

FIG. 4 illustrates a schematic view of the system of this invention applied to an adhesive joint in a composite pipe 19. The adhesive joint illustrated in FIG. 4 is a bell-and-spigot-type joint, where the spigot of the pipe 19 to the left inserts into the bell 20 of the pipe on the right. At the contact point between the spigot 19 and the bell 20, an adhesive layer 21 is provided, which is responsible for fastening one end to the other. Additionally, FIG. 4 illustrates a potential defect 25 in the joint, characterized by the absence of adhesive at a certain point in the union.

In the third embodiment, as in the first, at least one layer of carbon fiber 2 is provided inside the joint, so that it can receive an external thermal stimulus. Preferably, at least one layer of carbon fiber 2 is provided in the adhesive layer 21 (illustrated in the upper part of FIG. 4) and/or between the layers of the structure of the spigot of the pipe 19 (illustrated in the lower part of FIG. 4).

Just as in the first embodiment, preferably, the first electric cable 6 connects the carbon fiber layers 2 (optionally by means of a thermal connector) to the power source 5. Additionally, and also preferably, the second electric cable 7 connects the power source 5 to the electricity network (not shown).

During thermal excitation (heating), the joint is observed with a non-destructive inspection system 18, as illustrated in FIG. 4. As in the first embodiment, non-destructive inspection may be conducted by means of a shearographic system, a thermographic camera or both.

Preferably, the composite material used in the repair of this invention comprises matrix and reinforcement material. More preferably, the matrix material is a plastic or a resin, while the reinforcement material may be, for example, fiberglass.

FIG. 5 shows a result obtained from a thermographic inspection performed in a testing body containing three internal defects (continuous arrows). The dotted arrow indicates the internal source of the thermal excitation. The result clearly shows the presence of three internal defects.

Thus, this invention provides a low-cost system for inspecting repairs or joints of composite material applied to a structure (pipes, for example), which considerably improves the efficacy of thermographic or shearographic inspection methods.

Several variations on the scope of protection of this request are permitted. Accordingly, it should be emphasized that this invention is not limited to the specific configurations/embodiments described above. 

1. System for inspecting a repair or joint made of composite material applied to a structure, wherein at least one element that excites or is excited by a thermal and/or vibrational stimulus, with at least one exciter or excitable element being built into the repair or joint.
 2. System, according to claim 1, wherein a repair or a joint of composite material comprising matrix and reinforcement material.
 3. System, according to claim 2, wherein the matrix material being a plastic or resin and the reinforcement material being fiberglass.
 4. System, according to claim 1, wherein the exciter element being a piezoelectric actuator embedded inside the repair or joint, where the actuator is adapted to receive an external signal and to vibrate at least at a certain frequency.
 5. System, according to claim 4, wherein as comprising a set of piezoelectric actuators embedded in the extremities of the repair or joint.
 6. System, according to claim 5, wherein as additionally comprising at least one connector adapted to send the external signal to each one of the piezoelectric actuators.
 7. System, according to claim 1, wherein the excitable element being at least one layer of material that is excited by a thermal and/or vibrational stimulus.
 8. System, according to claim 7, wherein at least one layer of a material that is excited by a thermal and/or vibrational stimulus comprising at least one layer of carbon fiber.
 9. System, according to claim 8, wherein comprising at least one thermal connector adapted to connect to each of the carbon fiber layers to a power source.
 10. System, according to claim 2, wherein the exciter element being a piezoelectric actuator embedded inside the repair or joint, where the actuator is adapted to receive an external signal and to vibrate at least at a certain frequency.
 11. System, according to claim 3, wherein the exciter element being a piezoelectric actuator embedded inside the repair or joint, where the actuator is adapted to receive an external signal and to vibrate at least at a certain frequency.
 12. System, according to claim 2, wherein the excitable element being at least one layer of material that is excited by a thermal and/or vibrational stimulus.
 13. System, according to claim 3, wherein the excitable element being at least one layer of material that is excited by a thermal and/or vibrational stimulus. 